The long-term effects of cannabis have been the subject of ongoing debate.
Because cannabis is illegal in most countries, clinical research presents a
challenge and there is limited evidence from which to draw conclusions. In
2017, the U.S. National Academies of Sciences, Engineering, and Medicine
issued a report summarizing much of the published literature on health effects
of cannabis, into categories regarded as conclusive, substantial, moderate,
limited and of no or insufficient evidence to support an association with a
particular outcome.
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